Resins with various characteristics are used in the production of electric and electronic goods. Many such goods are becoming increasingly specialized and are also increasing in size, and yet are advantageously light weight. Electric and electronic goods should also have good scratch-resistance to maintain the appearance of the goods and good flame retardancy.
One method for achieving scratch-resistance and flame retardancy is to alloy a polycarbonate resin with a methacrylate, preferably a polycarbonate resin with polymethyl methacrylate (PMMA).
Polycarbonate resin is widely used in the production of electric or electronic goods, automobiles and other products because the resin has desirable properties such as good mechanical strength, transparency, heat stability, self extinction, dimension stability, and the like. Also polycarbonate resin can be rendered flame retardant using smaller amounts of flame retardant as compared with other conventional polymers because the chemical structure of polycarbonate resin lends itself to good flame retardancy.
However, the scratch-resistance of polycarbonate resin is not good, that is, about B grade of pencil hardness. Therefore, good scratch-resistance cannot be obtained with polycarbonate resin only.
Although polymethyl methacrylate resin has good scratch-resistance, generally about 3H grade of pencil hardness, it can be difficult to impart the desired degree of flame retardancy to the resin using conventional flame retardants.
Korean Patent Application No. 2006-111868 discloses a blend with good scratch-resistance as well as flame retardancy comprising polycarbonate resin and an alkyl (meth)acrylate such as polymethyl methacrylate. However, the polycarbonate resin is not highly compatible with the polymethyl methacrylate. Accordingly the blend separates into its respective phases even though the blend is processed at a high temperature. Further, the refraction index of polycarbonate resin is 1.59 and that of PMMA is 1.49. Thus, the alloy of polycarbonate resin and PMMA cannot obtain a bright color by light scattering, and the alloy shows an apparent weld line which is a defect. Accordingly, the blend is still not adequate for the production of electric or electronic goods.
Korean Patent Publication No. 2004-79118 discloses using a metal stearic acid ester to reduce the molecular weight of polycarbonate resin during the blending process in order to improve the compatibility of polycarbonate resin and PMMA. However, the blend exhibits poor mechanical properties.
U.S. Pat. No. 4,287,315 teaches polymer blends with improved impact strength consisting of polyamide and a high molecular weight olefinic copolymer. However, the blends have limited transparency.
U.S. Pat. No. 4,027,073 discloses an article comprising a solid substrate coated with a pigment free coating composition. In the patent, an additional coating process is required.